Experiences with RIHSA encephalography.

CONVENTIONAL neuroradiological techniques allow accurate location and fairly accurate identification of intracranial masses. Unfortunately, these procedures necessitate admission to hospital, cause some discomfort, and are not free from danger. Moreover, carotid angiography cannot reliably demonstrate lesions situated posteriorly in the hemispheres and, as it relies mainly on the detection of displaced vessels rather than on outlining the tumour itself, it is apt to miss or underestimate the size of infiltrating gliomas. Because of these disavan'tages, substances known to stain tumours or to be sdleotively concentrated in 'them have been studied in the hope of finding a means of outlining the tumour itself. Fluorescein is one such substance. Over 50 years ago it was being used as a vehicle for selenium in chemotherapy (von Wasserman, Keysser and Wassermann, 191 1) and more recently it has been used to delineate neoplastic tissue in exposed brain (Moore, 1947). Attempts were then made to detect fluorescein tagged with radioactive iodine through the intact skull, using a Geiger-Muller counter (Moore, 1948). These early attempts at cerebral scanning